The present invention relates to a hydraulic damper for an electromechanical valve utilized in a reciprocating piston internal combustion engine. In particular the present invention relates to a hydraulic damper that can provide relatively soft seating of an engine valve on an engine valve seat.
With a conventional mechanical engine valve-train system, the profile of the cam controls the valve to have seating velocity in a range that ensures soft seating at low engine speeds while maintaining reasonably fast closing and opening rates for good high speed volumetric efficiency. This range is typically designed using a 15-18 Î¼ m/degree cam ramp over the expected range of valve lash. The valve seating velocity (m/s) in a camshaft driven valve system is then proportional to the engine speed (rpm).
One of the significant challenges with electromechanical valve actuation systems is to replicate this engine speed dependant “soft seating” feature repeatably over all operating conditions and at low cost. Hydraulic damping has been identified as an effective approach to reduce the valve and armature impact velocity for electro-mechanically actuated valve trains. However, the damping does not provide engine speed dependant seating velocity. Additionally, the damper performance changes with oil temperature.
It is desirable to provide an apparatus and method of utilization thereof wherein a variable valve seating velocity can be achieved in a mechanical valve for different oil temperatures and engine speeds by varying the damper leakage flow area.